There is at present a widespread demand for display devices utilizing electrochromic display cells, for use in various types of electronic equipment. It has been difficult hitherto, however, to apply such electrochromic display cells to miniature electronic devices such as electronic wristwatches, because it has not been possible to ensure a sufficiently low level of power consumption. This is due to the fact that when a display segment has been set into a condition of coloration, by momentarily applying a potential between the corresponding segment electrode and the common electrode of the electrochromic display cell, thereby causing a current to momentarily flow between them, it has not been possible to ensure that the segment electrode is thereafter held in an electrically isolated condition with respect to the drive circuitry to which it is coupled. Thus, although no power is actually required in order to maintain the coloration condition of a segment once that condition has been established, since the charge developed on the capacitance between the segment electrode and the common electrode will act to maintain the coloration condition, in actual practice this charge is dissipated, in prior art electrochromic display devices, due to current leakage from the segment electrode after the coloration condition has been established.
With the present invention, such leakage of charge on the segment electrode is eliminated, thereby permitting a coloration condition of a display segment in an electrochromic display cell to be memorized over a long period of time without the necessity to supply power to the display cell in order to maintain the coloration condition. As a result, the power consumption of an electrochromic display device according to the present invention is substantially lower than that of prior art electrochromic display devices, making such a device suitable for use in miniature electronic devices such as electronic wristwatches.